Portion of a shoe midsole



FIG. 1 is a first perspective view of a portion of a shoe midsole showing our new design;

FIG. 2 is a second perspective thereof; and,

FIG. 3 is a side view thereof.

The uneven broken line immediately adjacent to the shaded area represents an unclaimed boundary of the design. The uneven broken line showing of the remainder of the shoe is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a portion of a shoe midsole, as shown and described. 